Using your index finger you inscribe the symbols into the soft surface of the square, but, as soon as you remove your hand, the symbols fade. Suddenly a crackling surge of electrical power arcs from a slot in the portal’s stone surround. It catches you full on the chest and flings you several feet through the air: lose 10 ENDURANCE points.
If you survive this severe shock, turn back to 25 and study the remaining symbols very carefully before you attempt to open the door again.